Dynamo coefficients from local simulations of the turbulent ISM

Details Dynamo coefficients from local simulations of the turbulent ISM Dynamo coefficients from local simulations of the turbulent ISM

2008-01-25

arxiv.org/abs/0801.4004v2

Astronomy and Astrophysics

Astrophysics

6 pages, 3 figures, to be published in AN

Scientific paper

10.1002/asna.200811005

Observations in polarized emission reveal the existence of large-scale coherent magnetic fields in a wide range of spiral galaxies. Radio-polarization data show that these fields are strongly inclined towards the radial direction, with pitch angles up to $35\degr$ and thus cannot be explained by differential rotation alone. Global dynamo models describe the generation of the radial magnetic field from the underlying turbulence via the so called $\alpha$-effect. However, these global models still rely on crude assumptions about the small-scale turbulence. To overcome these restrictions we perform fully dynamical MHD simulations of interstellar turbulence driven by supernova explosions. From our simulations we extract profiles of the contributing diagonal elements of the dynamo $\alpha$-tensor as functions of galactic height. We also measure the coefficients describing vertical pumping and find that the ratio $\hat{\gamma}$ between these two effects has been overestimated in earlier analytical work, where dynamo action seemed impossible. In contradiction to these models based on isolated remnants we always find the pumping to be directed inward. In addition we observe that $\hat{\gamma}$ depends on whether clustering in terms of super-bubbles is taken into account. Finally, we apply a test field method to derive a quantitative measure of the turbulent magnetic diffusivity which we determine to be ~ 2 kpc kms.

Affiliated with

Also associated with

No associations

Rating

Dynamo coefficients from local simulations of the turbulent ISM does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Dynamo coefficients from local simulations of the turbulent ISM, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dynamo coefficients from local simulations of the turbulent ISM will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-413248